I've recently stumbled across an issue with my 1978 Zaccaria Queens Castle where the 100 and 1000 point reels energise and occasionally stick with the coil buzzing the whole time until the machine eventually vibrates enough for it to stop. The 100 and 1000 point relays also hold on when this occurs.

I've checked the reels themselves and cleaned and adjusted the switches, I've checked the point relays and can't see anything particularly wrong. I've also looked at the whole playfield to check for any stuck switches or badly adjusted targets and then the score motor with no luck.

Any suggestions for a fix would be appreciated as I was planning to put this machine in a location next week.

Thank you,
James